What belongs to mineral acids. Fundamentals of mineral acid technology (for example, sulfuric acid)
Hydrofluoric acid is an inorganic acid. Chemical name - hydrogen tetrafluoroborate; formula H.
In production, it is obtained by chemical synthesis of hydrofluoric acid with boron oxide or hydroxide, as well as by dissolving boron trifluoride BF3 in water. In the laboratory, this acid can be obtained by mixing dry boric acid and 40% hydrofluoric acid solution. The reaction is exothermic. Requires the adoption of safety measures: the solution is poured into the powder gradually, with constant stirring. For mixing, use a stick made of ebonite or vinyl plastic. The procedure is carried out in a fume hood.
Properties
Under normal conditions, acid can exist only in solutions (in water, toluene, etc.). Miscible with water, soluble in ethyl alcohol... In its pure form, the compound is chemically unstable. Solutions are clear, colorless, or may have a slightly yellowish tint. The smell is absent or weak, specific, acidic. Hot solutions decompose with the formation of toxic oxofluoroboric acids. Toxic to humans and the environment. Corrosive to fabrics, corrosive to metals. Does not burn, does not explode.
Chemically a very strong acid. Interacts with metals and alkalis to form salts - tetrafluoroborates. The reaction with alkalis is violent. It easily reacts with metal salts and oxides, cyanides, ammonium salts, urea, with many organic compounds, for example, with diazo compounds (containing an organic radical connected to a nitrogen molecule), propylene, formaldehyde, ammonia. Reacts actively with oxidants.
Precautionary measures
The substance belongs to the second class of hazard. Flameproof, but when heated gives off hazardous gases such as hydrogen fluoride, fluorine. Reaction with an oxidizing agent can lead to fire and even explosion. Interaction with metal leads to the release of flammable hydrogen. Sealed acid containers may explode when heated due to decomposition gases.
A fire, in the zone of which there are containers with acid, can be extinguished with water, carbon dioxide, powder fire extinguishers. Every precaution should be taken to prevent the release of the reagent into the environment.
Being a strong acid, hydrogen tetrafluoroborate is dangerous to humans: it irritates the respiratory tract, causes severe, poorly healed chemical burns in contact with skin and mucous membranes. Can be fatal if swallowed. Chemical reaction products with hydrofluoric acid are often toxic by inhalation.
The victim from contact with the reagent must be taken out into fresh air, thoroughly rinsed the affected areas with water, and artificial respiration must be given. Be sure to call an ambulance.
The work area should be equipped with general ventilation. Employees must use a full set of protective equipment: self-contained breathing apparatus with air filtration; clothing recommended for contact with this acid; tight-fitting safety goggles; corrosion resistant rubber gloves. The use of contact lenses is not recommended.
Can be stored in glass containers at room temperature. Store in warehouses at a temperature not exceeding +30 ° C in sealed plastic containers.
When spilled, the acid is neutralized with calcium carbonate, industrial soda (sodium carbonate), quicklime (calcium oxide).
Waste disposal must be carried out by licensed organizations.
Application
Inorganic acid production. Features of storage and use. Fire hazard of inorganic acids
CONTENT
Introduction _________________ _______________________3
- Inorganic acid production ____________ 7
Nitric acid _______________________ _____7
Sulfuric acid__ ___________________________8
- Application of inorganic acids _____________ 10
Nitric acid _______________________ ____10
Sulfuric acid__ __________________________11
- Features of storage of inorganic acids _____ 13
Nitric acid _______________________ ______19
Sulfuric acid__ ____________________________20
- Fire hazard of inorganic acids ________ 24
Nitric acid _______________________ ______26
Sulfuric acid__ ____________________________27
Conclusion _______________ _________________________29
Bibliography _____________ _________________________30
INTRODUCTION
Inorganic acids- inorganic substances, whose molecules at electrolytic dissociationcleave off in the aquatic environment protons , as a result of which hydronium -cations H 3 O + and anions of acid residues A:
- HA + H 2 O - H 3 O + + A (1)
- H 3 BO 3 + 2H 2 O - - + H 3 O +
- HNO 3 + NaOH> NaNO 3 + H 2 O
- 2HCl + CaO> CaCl 2 + H 2 O
Inorganic acids are subdivided into oxygen-containing (oxoacids) of the general formula H n EO m, where E is an acid-forming element, and anoxic H n X, where X is halogen, chalcogen or an inorganic oxygen-free radical (CN, NCS, N 3, etc.). Oxo acids are characteristic of many chemical elements, especially for elements in high (+3 and higher)oxidation states.
The H atoms in oxo acids are usually associated with oxygen. If the oxo acid contains H atoms that are not bonded to oxygen (for example, two H atoms forming P-H bonds in H 3 PO 2), then they are not cleaved in an aqueous solution to form H 3 O + and do not take part in the reaction of acids with bases. Some acids are known in two tautomeric forms, differing in the position of the H atom, for example:
The molecules of many acids contain more than one atom of the acid-forming element E. There are very numerous isopolyacids containing E atoms linked through an oxygen atom, and the -E-O-E- fragments can form as open chains (for example, in H 4 P 2 O 7), and cyclic structures [for example, in (NRO 3) n]. Some acids contain chains of identical atoms, for example, the -S-S- chains in polythionic acids H 2 S n O 6 or sulfanes H 2 S n. Knownheteropolyacidshaving fragments -E-O-E "-, where E and E" are atoms of two different elements, for example: H 4? 14H 2 O. There are many complex acids, for example: H 2, H, H 4. Acids similar to oxo acids, but containing sulfur instead of the oxygen atom (s), are called thioacids, for example H 2 S 2 O 3, H 3 AsS 3. Peroxo acids such as H 2 S 2 O 8 have peroxo groups —O — O—.
The equilibrium constant of reaction (1) is called the acidity constant Ka. Polybasic acids dissociate stepwise, each step has its own K a, and always K a (1) "K a (2), approximately each subsequent Ka is 5 orders of magnitude less than the previous one. By the value of рК 1 = -lgK a (1) Inorganic acids are divided into very weak, weak, medium strength, strong, very strong According to Pauling's rule, for very weak oxoacids НnЭOm the difference m - n = 0, for weak, strong and very strong this difference is 1, 2, and 3, respectively. electron density from communication N-O to the E = O bonds (containing the O atom with a largeelectronegativity) and delocalization of electron density in the anion.
Characteristics of acids
To characterize the acidity of substances in non-aqueous media, useHammett acidity functionH 0. There are known liquids for which H 0 is more negative than for concentrated aqueous solutions of very strong acids, such as HNO 3, H 2 SO 4. These liquids are called super acids. Examples: 100% H 2 SO 4 (H 0 =? 12), anhydrous fluorosulfonic acid HSO 3 F (H 0 =? 15), a mixture of HF and SbF 5, (H 0 =? 17), 7% solution of SbF 5 in HSO 3 F (Н 0 = −19.4). An equimolar mixture of HSO 3 F and SbF 5 is called "magic acid". Superacidity is due to the exceptional weakness of interaction with the proton of the corresponding anions (HSO 4 -, SbF 6 -, etc.). Substances that usually do not exhibit basic properties, in particular hydrocarbons, are protonated in a superacid environment. This phenomenon is used in practice, mainly in organic synthesis (Friedel-Crafts alkylation, hydrogenation of oil, etc.).
Many oxo acids (HNO 3, HMnO 4, H 2 Cr 2 O 7, HClO, etc.) are strong oxidizing agents. The oxidative activity of these acids in an aqueous solution is more pronounced than that of their salts. All peroxo acids are strong oxidizing agents. Inorganic acids are always less thermally stable than their salts formed by active metals ( Na, K and etc.). Some acids ( H 2 CO 3, H 2 SO 3, HClO and others) it is impossible to isolate in the form of individual compounds, these acids exist only in solution.
General methods of obtaining acids
1.interaction of oxides (anhydrides) with water, for example:
- Р 2 O 5 + Н 2 O> Н 3 РО 4
- CaF 2 + H 2 SO 4> CaSO 4 + 2HF
- PI 3 + 3H 2 O> H 3 PO 3 + 3HI
- Al 2 Se 3 + 6H 2 O> 2Al (OH) 3 + 3H 2 Se
Application
Acids are used in industry and research. Produce in large quantities sulfuric acid, nitric acid, hydrochloric acid, etc.
- PRODUCTION OF INORGANIC ACIDS
Hydrochloric acid is obtained by dissolving gaseous hydrogen chloride in water. Hydrogen chloride get by burning hydrogen in chlorine ... In laboratory conditions, a method developed by alchemists is used, which consists in the action of strong sulfuric acid on table salt:
- NaCl + H 2 SO 4 (conc.) (150 ° C)> NaHSO 4 + HCl ^
- NaCl + NaHSO 4 (> 550 ° C)> Na 2 SO 4 + HCl ^
Nitric acid
The modern method of its production is based on the catalytic oxidation of synthetic ammonia on platinum - rhodium catalysts (Haber method) to a mixture of nitrogen oxides (nitrous gases), with their further absorption water
- 4 NH 3 + 5 O 2 (Pt)> 4 NO + 6 H 2 O
- 4 KNO 3 + 2 (FeSO 4 7H 2 O) (t °)> Fe 2 O 3 + 2 K 2 SO 4 + 2HNO 3 ^ + NO 2 ^ + 13 H 2 O
- KNO 3 + H 2 SO 4 (conc.) (T °)> KHSO 4 + HNO 3 ^
Sulphuric acid
Structural formula sulfuric acid
Raw materials for obtaining sulfuric acid are sulfur, metal sulfides, hydrogen sulfide , waste gases from thermal power plants, sulfates of iron, calcium, etc.
Main stages
The main stages of obtaining sulfuric acid:- Roasting of raw materials to obtain SO 2
Oxidation of SO 2 to SO 3
SO 3 absorption
Following are the reactions for the production of sulfuric acid from a mineral pyrite on a catalyst - vanadium (V) oxide.
- 4 FeS 2 + 11 O 2 = 2 Fe 2 O 3 + 8 SO 2
2SO 2 + O 2 (V 2 O 5)> 2 SO 3
Nitrous preparation method sulfuric acid
- SO 2 + NO 2> SO 3 + NO ^.
2 NO + O 2> 2 NO 2
Obtaining sulfuric acid (so-called vitriol oil) fromferrous sulfate- thermal decomposition of iron (II) sulfate with subsequent cooling of the mixture
- 2 FeSO 4 7H 2 O> Fe 2 O 3 + SO 2 + H 2 O + O 2
SO 2 + H 2 O + O 2? H 2 SO 4
- APPLICATION OF INORGANIC ACIDS
Industry
- Apply in hydrometallurgyand electroforming ( pickling, pickling ), for cleaning the surface of metals at soldering and tinning to obtain chlorides of zinc, manganese, iron and other metals. Mixed with Surfactant used for cleaning ceramic and metal products (here it is necessary inhibited acid) from dirt and disinfection.
V Food Industryregistered as a regulator acidity, food additive E507... It is used for manufacturingseltzer (soda) water.
The medicine
- Componentgastric juice; diluted hydrochloric acid was previously prescribed internally, mainly for diseases associated with insufficient acidity of gastric juice.
- production of nitrogen and complex mineral fertilizers
production of sodium, potassium, calcium nitrates
in hydrometallurgy
explosives production
production of sulfuric and phosphoric acids
obtaining aromatic nitro compounds
production of dyes
is part of rocket fuel
etching and dissolution of metals in metallurgy
etching of semiconductor materials
A mixture of concentrated nitric and hydrochloric acids (ratio by volume 1: 3) is called aqua regia, it dissolves even noble metals. A mixture of HNO3 with a concentration of about 100% and H 2 SO 4 with a concentration of about 96% at a ratio by volume of 9: 1 is called melange.
Sulphuric acid- production of mineral fertilizers
electrolyte in lead-acid batteries
obtaining various mineral acids and salts, chemical fibers, dyes
production of smoke and explosives
petroleum, metalworking, textile, leather industries
in the food industry - registered as food additive E513(emulsifier);
- dehydration (obtaining diethyl ether, esters)
hydration (ethanol from ethylene), sulfonation (synthetic detergents and intermediates in the production of dyes)
alkylation (obtaining isooctane, polyethylene glycol, caprolactam)
sulfonation ( synthetic detergentsand intermediate products in the production of dyes)
- STORAGE FEATURES
Wherever possible, aggressive acids should be replaced with others that are less hazardous; it is necessary to use the minimum concentration allowed for the process. When using mineral acids, appropriate safety measures must be observed during storage, transportation, disposal, and adequate ventilation, personal protective equipment and first aid measures must be provided.
Storage... Acid storage rooms should be isolated from others, well ventilated and protected from sunlight and heat sources; they must have a cement floor and be free from materials with which the acid could react. Large warehouses should be surrounded by fences to collect acid in case of spills and provided with neutralization facilities. A fire hydrant and self-contained breathing equipment should be located outside the acid storage area in case of emergency and rescue operations. Leaks must be cleaned up immediately by flushing with a jet of water; in the event of a large leak, personnel must leave the room and then neutralize the acid. Electrical equipment must be waterproof and acid resistant. It is advisable to use safe lighting.
Containers should be kept tightly closed and clearly marked so that their contents are known. Pipes, connections, seals and valves should be made of acid-resistant materials. Glass or plastic containers must be reliably protected from impacts; they should be lifted off the floor to facilitate flushing in the event of a leak. Cylindrical containers should be stored on racks and secured. Anhydride gas cylinders must be stored upright and capped. It is preferable to store empty and full containers separately.
Transportation... Acids must be supplied through sealed systems to avoid contact with them. When transporting containers, it is necessary to use the appropriate equipment, and work to be carried out by qualified personnel. Decanting should only be carried out by means of special siphons, pumps, devices for tilting cylindrical containers or bottles, etc. Anhydrous anhydride cylinders must be fitted with special drain valves and fittings.
When mixing acids with other chemicals or water, workers must be clear about the fact that an intense reaction can occur. In order to avoid excessive heat generation and violent reactions that can cause splashes and contact of acid on the skin or eyes, the concentrated acid must be added slowly to the water, and not vice versa.
Ventilation... Where aerosols or acid vapors are generated, for example during electroplating, good ventilation must be provided.
Individual protection... People who come into contact with splashes of mineral acids should use acid-resistant personal protective equipment: protecting hands, eyes, face, use aprons, overalls and protective suits.
When workers need to enter a tank containing acids for maintenance or repairs, clean the tank first and take all confined space precautions listed elsewhere in this section. Encyclopedias.
Education. All workers handling acids must be instructed in their hazardous properties. Certain types of work, for example, carried out in confined spaces or those in which it is involved a large number of acids must be produced by two workers, one of whom is always ready to help the other in case of need.
Sanitation... Personal hygiene is paramount when coming into contact with inorganic acids. Workers are required to provide adequate sanitation and wash thoroughly at the end of their shift.
Urgent care... If acids come into contact with skin or eyes, rinse immediately and abundantly with running water. Therefore, rooms should be equipped with showers, eyewash fountains, bathtubs or water tanks. Contaminated clothing should be removed and skin cleansed. The usual procedure is to neutralize contaminated skin with 2-3% sodium bicarbonate solution, 5% sodium carbonate solution and 5% sodium hyposulfite solution, or 10% triethanolamine solution.
Persons who inhale acid vapors should be immediately removed from the contaminated area, ensured rest and medical attention. In case of accidental ingestion of acid, it is necessary to give a neutralizing agent and rinse the stomach. Do not artificially induce vomiting.
Medical supervision... Workers must undergo a medical examination before hiring and periodically during work. Medical examination before employment should be aimed mainly at identifying chronic diseases of the gastrointestinal tract, skin, eyes, respiratory and nervous system... Periodic checks should be carried out at short intervals and include checking the condition of the teeth.
Hydrochloric acid
Technical synthetic hydrochloric acid is poured into special gummed tanks of the sender or recipient, gummed containers, polyethylene barrels with a capacity of 50 dm 3 and glass bottles with a capacity of 20 dm 3 in accordance with the current regulatory documentation.
Glass bottles are packed in boxes of the V-1 type, number 3-2 in accordance with GOST 18573. The packaging must comply with GOST 26319.
It is allowed to pour the product into tanks and containers with the remainder of hydrochloric acid, if the analysis of the remainder confirms the compliance of its quality with the requirements of this standard, Otherwise, the remainder of hydrochloric acid is removed, and the tank or container is washed.
Barrels and bottles must be dry and clean.
The filling hatches of tanks, containers and barrel caps must be sealed with rubber or polyethylene gaskets, both when shipped to consumers (filled with acid) and when empty containers are returned to the supplier.
etc.................
Sulphuric acid. Under normal conditions, concentrated sulfuric acid is a heavy, oily liquid, colorless and odorless, with a sour "copper" taste. Mixes up with water in any ratio with the release of heat. Sulfuric acid is not volatile, but at temperatures above 50 ° C it is capable of forming sulfuric anhydride vapors, which is more toxic than the acid itself.
In industry, it is produced in the form of a monohydrate - 98% sulfuric acid solution; oleum - 20% solution of sulfuric anhydride SO 3 in sulfuric acid; crude sulfuric acid (vitriol oil) - 93-97% sulfuric acid solution.
Sulfuric acid is used in almost any field of industry: in the production of mineral fertilizers; as electrolyte in lead-acid batteries; for obtaining various mineral acids and salts; in the production of chemical fibers, dyes, smoke and explosives; in the oil, metalworking, textile, leather and other industries; in the food industry ( food supplement E 513), in industrial organic synthesis (in reactions: dehydration, hydration, sulfonation, alkylation, etc.), for the recovery of resins in filters in the production of distilled water.
The main routes of entry of sulfuric acid into the body are oral, inhalation and percutaneous. Lethal dose it is considered to be 5 - 10 g.
With inhalation poisoning, difficulty breathing is observed, which is accompanied by cough, hoarseness, possibly the development of laryngitis, bronchitis or tracheitis. When high concentrations are inhaled, edema of the larynx and lungs develops, asphyxia and shock may develop. The latent period of sulfuric acid poisoning can be up to 90 days.
When sulfuric acid gets on the skin, it quickly penetrates deep into the tissues, first forming white, and, with the passage of time, brown-black scabs.
During the pathological examination of oral poisoning, traces of a chemical burn around the mouth (brown stripes and spots) are observed, the mucous membranes of the mouth, pharynx, esophagus are painted gray-brown, the gastric mucosa is grayish-red.
Qualitative and quantitative analysis for the presence of sulfuric acid.
When examining the dialysate for the presence of sulfuric acid, it is distilled over copper sawdust and the distillation is collected in a receiver containing a solution of iodine in potassium iodide.
In the flask, a redox reaction takes place with the formation of sulfurous acid, and then its decomposition to sulfur oxide (II).
Sulfur oxide with water vapor, getting into the receiver, interacts with the iodine solution to form sulfuric acid.
During simple distillation, due to the constant presence of chlorides extracted from the biological object, they react with free sulfuric acid to form hydrogen chloride.
The sulfuric acid formed as a result of distillation is detected by the reactions:
ü Barium sulfate formation reaction. The appearance of a white precipitate upon addition of barium chloride indicates the presence of sulfate ions, but does not prove the presence of free sulfuric acid.
ü The reaction of obtaining lead sulfate. Precipitation of a white precipitate, insoluble in nitric acid, but soluble in alkali solutions and ammonium acetate solution.
ü Reaction with barium rhodizonate. The reaction is based on the fact that sodium rhodizonate with barium salts forms barium rhodizonate, which has a red color. From the addition of sulfuric acid or barium sulfate ions, rhodizonate decomposes, a white precipitate of barium sulfate is formed, and the red color disappears.
The reaction is specific to the sulfate ion. Test for the presence of free sulfuric acid.
quantitation sulfuric acid is carried out by the method of alkalimetry. A 0.1 M sodium hydroxide solution (methyl orange indicator) is used as a titrant.
Hydrochloric acid. Colorless (technical hydrochloric acid, yellowish due to impurities of Fe, Cl 2, etc.) caustic liquid with a pungent odor, containing 35 - 38% hydrogen chloride. It evaporates easily in air, "smokes" due to the formation of hydrogen chloride with water vapor of fog droplets. Mixes up with water in any ratio.
The industry produces "battery" hydrochloric acid containing about 37% hydrogen chloride and concentrated hydrochloric acid containing about 25% hydrogen chloride.
It is used in chemical synthesis, hydrometallurgy and electroplating (for processing ores, etching metals), for cleaning the surface of metals during soldering and tinning, for obtaining chlorides of zinc, manganese, iron and other metals. Mixed with surfactants, it is used for cleaning ceramic and metal products from contamination and disinfection. In the food industry, it is registered as an acidity regulator and food additive E 507. Hydrochloric acid is a natural component of human gastric juice. Hydrochloric acid solutions, 0.3 - 0.5%, usually mixed with the enzyme pepsin, are administered orally to patients with insufficient acidity.
The main route of intake of hydrochloric acid is inhalation, less often percutaneous and oral. A lethal dose is considered to be 10-15 g of hydrochloric acid.
When hydrogen chloride is inhaled, irritation of the upper respiratory tract and lungs is observed, manifested by hoarseness, coughing, and chest pain. In severe cases, death occurs from asphyxia as a result of laryngeal edema or spasm of the glottis after 3 to 4 hours.
With percutaneous and oral poisoning, the symptoms are similar to those of sulfuric acid poisoning, but to a lesser extent. Serous inflammation with blisters is observed on the skin, the affected areas have a gray-whitish color, the burns are minor. In contact with the mucous membrane of the eye, it causes conjunctivitis, chemical burns, corneal opacity.
At postmortem examination, a grayish or black color of the mucous membranes of the oral cavity, esophagus, stomach and upper section intestines. The contents of the stomach are a brownish mass. The liver, kidneys and heart are prone to fatty degeneration. The heart muscle is flabby and yellowish in color.
Qualitative and quantitative analysis for the presence of hydrochloric acid.
An aqueous extract from a biological material, or dialysate, is initially examined for the presence of chloride ions. The formation of an abundant white precipitate with silver nitrate indicates the need for further testing for free hydrochloric acid.
Due to the possibility of the formation of hydrochloric acid from chlorides in the presence of free sulfuric acid, a study is first carried out for sulfuric acid, and then for hydrochloric acid.
When examining the dialysate for the presence of hydrochloric acid, it, like hydrochloric acid, is obtained by distilling the dialysate in a sand bath. Initially, water is distilled off from the flask into the receiver, and when hydrogen chloride reaches 10% concentration, it begins to be distilled into the receiver and dissolves in the water present. If possible, distillation is carried out until all of the liquid in the flask has evaporated.
The distillate is examined for the presence of hydrogen chloride by the following reactions:
ü Reaction with silver nitrate. The appearance of a white precipitate, which is soluble in ammonia solution and formed again upon the addition of nitric acid, indicates the presence of chloride ions.
ü Iodine release reaction. When potassium chlorate is added to the distillate with slight heating, free chlorine is released, which is detected by the bluing of starch iodine paper.
Quantitation.
The quantitative determination of hydrogen chloride is important in order to judge whether in this case (for example, in the vomit) there is an introduced acid, and not hydrochloric acid of gastric juice (0.1-0.2%), which is usually already in the stomach contents of a corpse. neutralized.
A certain part of the aqueous extract is subjected to distillation, evaporating the contents of the flask, as described above, to dryness. The amount of hydrogen chloride in the distillate is determined by Volhard titration or by weight, weighing silver chloride.
The Volhard method is not applicable to the quantitative determination of hydrochloric acid if the biological material is subject to decay. The resulting hydrogen sulfide reacts with silver nitrate to form a precipitate of silver sulfide (AgS) and distorts the analysis results. Therefore, for the quantitative determination of hydrochloric acid in stale biological material, the method of gravimetry is used.
An excess of silver nitrate is added to the solution, the resulting precipitates of chloride and silver sulfide are filtered off and treated with a 10% ammonia solution to dissolve silver chloride. The ammonia solution is acidified with nitric acid, and the separated precipitate of silver chloride is filtered off, dried and weighed.
Nitric acid. Colorless transparent liquid. Mixes up with water in any ratio. V open form Nitric acid gives off heavier vapors that form white smoke. Non-flammable, but has the ability to ignite all combustible substances. It can explode in the presence of vegetable and mineral oils, alcohol.
In industry it is produced in the form of 50 - 60% and 96 - 98% solutions.
Industrial application of nitric acid: in the production of mineral fertilizers; in the military industry (in the production of explosives, as an oxidizer for rocket fuel, in the synthesis of various substances, including poisonous ones); for etching printing plates; in the production of dyes and drugs (nitroglycerin); in jewelry (the main method for determining gold in a gold alloy).
As with the previous acids, the main routes of intake for nitric acid are inhalation, percutaneous, and oral. A lethal dose is considered to be 8-10 g of nitric acid.
Irritation of the upper respiratory tract and lung tissue leads to development toxic edema lungs. The latent period is from 3 to 6 hours. In case of inhalation poisoning, cyanosis of the mucous membranes of the eyelids and lips is observed, a large amount of fine-bubble foam accumulates in the trachea and bronchi, the lungs are enlarged, on the cut, the color of the lungs is bluish-red with a large accumulation of foam. Internal organs are full-blooded, there is swelling of mild meninges and the brain.
Upon contact with the skin, tissues acquire yellow due to decomposition and nitration products. When ingested, poisoning begins with sharp pains in the mouth, pharynx, esophagus, and stomach. Vomiting of brown masses with scraps of mucous membrane. Death is due to shock or collapse.
At postmortem examination, the contents of the stomach have a smell of nitrogen oxides, in the circumference and mucous membrane of the mouth, the mucous membrane of the digestive tract, a yellowish color is observed. The heart muscle and liver are grayish-red with a brown tinge, flabby.
Qualitative and quantitative analysis for the presence of nitric acid.
To detect nitric acid, the dialysate is distilled, as in the case of sulfuric acid, over copper sawdust, and water is placed in the receiver to trap the nitrogen oxide (IV) formed in the flask. When nitric acid interacts with copper sawdust, nitrogen oxide (II) is formed, which is oxidized to nitrogen oxide (IV), which reacts with water, resulting in a mixture of nitric and nitrous acids.
The detection of the formed nitric and nitrous acids is carried out according to the reactions:
ü Reaction with diphenylamine... The reaction is based on the oxidation of diphenylamine with nitric acid, in this case, colorless diphenylbenzidine is initially formed, which, upon further oxidation, turns into a blue compound. The reaction is nonspecific. The same coloration is given by salts of nitric and nitrous acids, as well as other oxidizing agents.
ü Reaction with brucin. The appearance of a red color indicates the presence of nitric acid.
BRUCIN
ü Reaction with protein for nitric acid (xanthan protein test). Free nitric acid, at a sufficient concentration, is capable of being fixed by proteins and staining them yellow, turning orange from the addition of ammonia. Woolen and silk threads will change their color as a result of this reaction, unlike cotton threads, which remain white.
Picric acid can give a similar color (yellowing of the threads), however, the color of the dialysate solution will also be yellow.
Reaction to nitrous acid. Green coloration when adding phenazone solution in the presence of sulfuric acid indicates the presence of nitrous acid in the dialysate.
quantitation nitric acid is carried out by the method of neutralization. 0.1M sodium hydroxide solution is used as a titrant, phenolphthalein is used as an indicator.
II. Caustic alkalis.
Caustic alkalis include sodium hydroxide (caustic soda, NaOH), potassium hydroxide (KOH) and calcium hydroxide Ca (OH) 2. A weak base is an ammonia solution (NH4OH).
Sodium hydroxide(caustic soda, caustic soda, caustic soda, caustic alkali)... White crystalline solid. It spreads out in the air, as it attracts moisture. It dissolves well in water with a large release of heat, forming solutions that are soapy to the touch. Soluble in alcohol and glycerin.
Sodium hydroxide is used in most industries and for domestic needs: in the pulp and paper industry; for saponification of fats in the production of soap, shampoos and other detergents; in chemical industries (for neutralizing acids and acid oxides, as a reagent or catalyst in chemical reactions, in chemical analysis for titration, for etching aluminum and in the production of pure metals, in oil refining for the production of oils); as an agent for dissolving blockages in sewer pipes; in civil defense for the degassing and neutralization of toxic substances; to clean the exhaled air from carbon dioxide; in food preparation (for washing and peeling fruits and vegetables, in the production of chocolate and cocoa, drinks, ice cream, coloring caramel, for softening olives and giving them a black color, in the production of bakery products, as a food additive E-524.
Routes of entry into the body: oral, inhalation (in the form of dust). The effect is especially pronounced in direct contact with the skin or mucous membranes. A pronounced irritating and cauterizing effect develops, as well as deep necrosis due to the formation of loose soluble protein albuminates. A lethal dose is considered to be 10 - 20 g of sodium hydroxide.
In contact with the skin or mucous membranes, a deep burn is typical with the formation of soft scabs and their subsequent scarring. With inhalation damage, an acute inflammatory process respiratory tract; possible pneumonia. When sodium hydroxide is ingested (orally), acute inflammation, small ulcers, burns of the mucous membranes of the lips, mouth, esophagus and stomach. Poisoning is accompanied by severe thirst, salivation, bloody vomiting, in severe cases it develops internal bleeding... Contact with the mucous membrane of the eyes is fraught with severe burns, up to the appearance of blindness.
Qualitative and quantitative analysis for the presence of sodium hydroxide.
The detection of sodium hydroxide is carried out on the Na + cation.
ü Reaction with potassium hydroxystibiate. In an acetic acid medium, when a solution of potassium hydroxystibiate is added to the dialysate, a white crystalline precipitate appears.
The rediscovery of sodium hydroxide is possible due to the formation of methoantimonic acid HSbO 3 in an acidic medium, which will precipitate.
ü Reaction with zinc uranyl acetate. In the presence of sodium ions in neutral and acetic acid media, zinc-uranyl acetate forms a crystalline precipitate of greenish-yellow color. Crystals are in the form of octahedra or tetrahedrons.
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quantitation sodium hydroxide is carried out by acidimetry, using a 0.1 M hydrochloric acid solution as a titrant, phenolphthalein as an indicator.
Potassium hydroxide (caustic potash, caustic potash). Colorless, very hygroscopic crystals, but less hygroscopic than sodium hydroxide. Aqueous solutions are strongly alkaline.
Industrial applications: in the food industry (food additive E525), for the production of methane, the absorption of acid gases and the detection of some cations in solutions, in the production of liquid soaps, for cleaning stainless steel products from grease and other oily substances, as well as mechanical processing residues , electrolyte in alkaline (alkaline) batteries.
Routes of entry into the body and symptoms of poisoning are similar to sodium hydroxide. Many reactions to the body are more pronounced than sodium hydroxide. A lethal dose is considered to be 10 - 20 g of potassium hydroxide.
Qualitative and quantitative analysis for the presence of potassium hydroxide.
The pronounced alkaline reaction of the dialysate environment, the absence of carbonates and the presence of potassium ions indicate the presence of potassium hydroxide in the material.
To detect potassium ions in dialysates, the following reactions are used:
ü Reaction with sodium hydrogen tartrate(NaHC 4 H 4 O 6) . The formation of a white precipitate indicates the presence of K +.
ü Reaction with sodium cobalt nitrite(Na 3 . In the presence of potassium ions, a yellow crystalline precipitate K 2 Nа [Сo (NO 2) 6] is formed.
These reagents give precipitation with potassium ions in neutral or weakly acidic solutions, therefore, dialysates with an alkaline reaction are neutralized or brought to a weakly acidic reaction (pH = 3-4) with a solution of acetic acid before the start of the study.
quantitation potassium hydroxide is carried out by acidimetry, using a 0.1 M hydrochloric acid solution as a titrant, phenolphthalein as an indicator.
Ammonia - a caustic, colorless gas with a pungent odor. Possesses high volatility. Very volatile. When ammonia is dissolved in water, ammonium hydroxide is formed. Ammonia water (ammonium hydroxide, ammonia water, caustic ammonium, caustic ammonia). Volatile liquid with a pungent specific odor. The toxicity in the air increases dramatically with increasing temperature and humidity.
A 25% ammonia solution is commercially available. The saturated solution contains 33% ammonia, and ammonia - 10%. Industrial use: in the food industry (food additive E 527); as a fertilizer.
The main route of ammonia intake is inhalation. A lethal dose is 10-15 ml of a 33% solution or 25-50 ml of a 10% solution.
At high concentrations in the air, there is profuse lacrimation, pain in the eyes, burns of the conjunctiva and cornea, loss of vision. From the respiratory tract - coughing attacks, sharp swelling of the tongue, burns of the mucous membranes of the upper respiratory tract with necrosis, laryngeal edema, bronchitis, bronchospasm. At very high concentrations, paralysis of the central nervous system and rapid death occurs with symptoms of asphyxia. Death occurs within 10 to 15 minutes.
Autopsy reveals bright red membranes of the mouth, pharynx, esophagus, stomach, pulmonary edema, changes in the kidneys (nephrosis and necrosis of the convoluted tubules), cerebral hemorrhage, and the smell of ammonia from internal organs.
Qualitative and quantitative analysis for the presence of ammonium hydroxide.
Analysis for ammonia is carried out if preliminary tests have indicated its possible presence.
Preliminary tests for ammonia are carried out with three indicator papers: red litmus, soaked in a solution of copper sulfate and soaked in a solution of lead acetate. Blue litmus paper and paper dipped in a solution of copper sulfate indicates the presence of ammonia.
Blackening of the "lead" paper indicates the presence of hydrogen sulfide and, consequently, the decay process. In this case, a study for the presence of ammonia is impractical. The formation of ammonia can also occur in the presence of alkalis (NaOH, KOH), which release ammonia from its salts and protein substances.
Reaction with Nessler's reagent. Yellow-brown or orange-brown coloration of the precipitated diiodimercurammonium precipitate indicates the presence of ammonia in the dialysate. The reaction is not specific, since many ions can form precipitates of this color in an alkaline medium in the presence of iodide ions.
quantitation ammonium hydroxide is carried out by acidimetry, using a 0.1 M hydrochloric acid solution as a titrant, methyl orange is the indicator.
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Inorganic (mineral) acids- inorganic substances with a complex physical and chemical properties which are inherent in acids. Substances of an acidic nature are known for most chemical elements with the exception of alkali and alkaline earth metals.
Most inorganic acids under normal conditions exist in a liquid state, some in a solid state (orthophosphoric, boric, tungsten, polysilicon (SiO 2 hydrates), etc.). Acids are also aqueous solutions of some gaseous compounds (hydrogen halides, hydrogen sulfide H 2 S, nitrogen dioxide NO 2, carbon dioxide CO 2, etc.). Some acids (for example, carbonic H 2 CO 3, sulfurous H 2 SO 3, hypochlorous HClO, etc.) cannot be isolated as individual compounds, they exist only in solution.
By chemical composition distinguish between anoxic acids (HCl, H 2 S, HF, HCN) and oxygen-containing (oxo acids) (H 2 SO 4, H 3 PO 4). The composition of anoxic acids can be described by the formula: H n X, where X is an acid-forming chemical element (halogen, chalcogen) or an oxygen-free radical: for example, hydrobromic HBr, hydrocyanic HCN, hydro azide HN 3 acids. In turn, all oxygen-containing acids have a composition that can be expressed by the formula: H n XO m, where X is a chemical element that forms an acid.
Hydrogen atoms in oxygen-containing acids are most often linked to oxygen by a polar covalent bond. Acids with several (more often two) tautomeric or isomeric forms are known, which differ in the position of the hydrogen atom:
Separate classes of inorganic acids form compounds in which the atoms of the acid-forming element form molecular homo- and heterogeneous chain structures. Isopolyacids are acids in which the atoms of the acid-forming element are linked through an oxygen atom (oxygen bridge). Examples are polysulfuric H 2 S 2 O 7 and H 2 S 3 O 10 and polychromic acids H 2 Cr 2 O 7 and H 2 Cr 3 O 10. Acids with several atoms of different acid-forming elements connected through an oxygen atom are called heteropoly acids. There are acids, the molecular structure of which is formed by a chain of identical acid-forming atoms, for example, in polythionic acids H 2 S n O 6 or in sulfanes H 2 S n, where n≥2.
This pattern is due to an increase in the polarization of the H – O bond due to the shift of the electron density from the bond to the electronegative oxygen atom along the mobile π-bonds E = O and the delocalization of the electron density in the anion.
Inorganic acids have properties common to all acids, including: color of indicators, dissolution of active metals with the evolution of hydrogen (except for HNO 3), the ability to react with bases and basic oxides to form salts, for example:
The number of hydrogen atoms split off from the acid molecule and capable of being replaced by a metal to form a salt is called the basicity of the acid. Acids can be divided into mono-, di- and tri-basic. Acids with a higher basicity are not known.
Many inorganic acids are monobasic: hydrohalogenic HHal, nitric HNO 3, chloric HClO 4, thiocyanic HSCN, etc. Sulfuric H 2 SO 4, chromic H 2 CrO 4, hydrogen sulfide H 2 S are examples of diacids, etc.
Polybasic acids dissociate stepwise, each step has its own acidity constant, and each subsequent K a is always less than the previous one by about five orders of magnitude. The dissociation equations for tribasic orthophosphoric acid are shown below:
Basicity determines the number of series of medium and acidic salts - acid derivatives.
Only the hydrogen atoms that are part of the hydroxy groups - OH are capable of replacement, therefore, for example, orthophosphoric acid H 3 PO 4 forms average salts - phosphates of the form Na 3 PO 4, and two series of acidic - hydrogen phosphates Na 2 HPO 4 and dihydrogen phosphates NaH 2 PO 4 . Whereas, in phosphorous acid H 2 (HPO 3) there are only two rows - phosphites and hydrophosphites, and in hypophosphorous acid H (H 2 PO 2) - only a number of intermediate salts - hypophosphites.
An exception is boric acid H 3 BO 3, which exists in an aqueous solution in the form of a monobasic hydroxo complex:
Modern theories of acids and bases significantly expand the concept of acidic properties. So, a Lewis acid is a substance whose molecules or ions are capable of accepting electron pairs, including those that do not contain hydrogen ions: for example, metal cations (Ag +, Fe 3+), a number of binary compounds (AlCl 3, BF 3, Al 2 O 3, SO 3, SiO 2). Protic acids are considered by the Lewis theory as a special case of the acid class.
All peroxo acids and many oxygen-containing acids (nitric HNO 3, sulfuric H 2 SO 4, manganese HMnO 4, chromic H 2 CrO 4, hypochlorous HClO, etc.) are strong oxidants. The oxidizing activity of these acids in aqueous solution is more pronounced than that of their salts; moreover, the oxidizing properties are greatly weakened by dilution of acids (for example, the properties of dilute and concentrated sulfuric acid). Inorganic acids are also always less thermally stable than their salts. These differences are associated with the destabilizing effect of the strongly polarized hydrogen atom in the acid molecule. This is most clearly manifested in the properties of oxygen-containing oxidizing acids, for example, perchloric and sulfuric. This also explains the impossibility of the existence of a number of acids outside the solution, given the relative stability of their salts. An exception is nitric acid and its salts, which exhibit strongly pronounced oxidizing properties, regardless of the dilution of the solution. This behavior is associated with the structural features of the HNO 3 molecule.
The nomenclature of inorganic acids has come a long way of development and evolved gradually. Along with the systematic names of acids, traditional and trivial ones are widely used. Some common acids can have different sources of different names: for example, an aqueous solution of HCl can be called hydrochloric acid, hydrochloric acid, hydrochloric acid.
Traditional Russian names for acids are formed by adding morphemes to the name of the element -naya or -new(chloric, sulfuric, nitrogen, manganese). For different oxygenated acids formed by one element, use - clean for a lower oxidation state (sulfurous, nitrogenous). In some cases, morphemes are additionally used for intermediate oxidation states -sweat and -sweet(see below the names of oxygenated chlorine acids).
The traditional names of some inorganic acids and their salts are given in the table:
For lesser known acids containing acid-forming elements in variable oxidation states, systematic names are usually used.
In the systematic names of acids, the suffix is added to the root of the Latin name of the acid-forming element -at, and the names of the remaining elements or their groups in the anion acquire the connecting vowel -o. The oxidation state of the acid-forming element is indicated in parentheses, if it has an integer value. Otherwise, the name also includes the number of hydrogen atoms. For example (traditional names in brackets):
HAuCl 4 - hydrogen tetrachloroaurate (III) (chloroauric acid)
Below are the roots Latin names acid-forming elements that do not coincide with the roots of the Russian names of the same elements: Ag - argent (at), As - arsen (at), Au - aur (at), Cu - cupr (at), Fe - ferr (at), Hg - merkur (at), Pb - plumb (at), Sb - stib (at), Si - silic (at), Sn - stann (at), S - sulf (at).
In the formulas of thioacids formed from oxyacids by replacing oxygen atoms with sulfur atoms, the latter are placed at the end: H 3 PO 3 S -
The third great achievement of chemistry in the XIII century - obtaining mineral acids... The first mentions of sulfuric and nitric acids are found in a Byzantine manuscript of the 13th century.
Even in antiquity, it was noticed that when alum or vitriol is heated, "sour vapors" are released. However, the production of sulfuric acid was first mastered only at the end of the 13th century. The books of Geber describe the experience of obtaining sulfuric and hydrochloric acids, as well as aqua regia.
For a long time, sulfuric acid was used only as a reagent in laboratories, and from the second half of the 18th century. it was used in handicraft practice - first for dyeing substances, and then also for bleaching. In 1744, the Saxon mountain councilor Barth of Freiberg discovered the process of sulfonation of indigo and used it for the first time to dye wool. In this regard, the demand for sulfuric acid has continuously increased and rational methods of its production have appeared. J. H. Bernhardt and H. I. Kohler organized several sulfuric acid plants, mainly in Saxony. These enterprises supplied sulfuric acid to Frankfurt, Bremen, Nuremberg, as well as outside Germany. At the end of the 18th century. in the Ore Mountains alone, 30 sulfuric acid plants operated. Almost simultaneously, the same factories appeared in Bohemia and Harz. The largest enterprises producing sulfuric acid belonged to the manufacturer Johann David Stark from Pilsen. Stark, an experienced cotton fiber specialist, was the first to understand the importance of sulfuric acid as an adjunct to cotton bleaching.
The rapid development of textile factories in the era of the industrial revolution, carried out thanks to the creation of weaving and spinning machines, became possible only in connection with the use of new chemical effective methods of bleaching and dyeing fabrics. The first English sulfuric acid factory was established in Richmond (near London) by Dr. Ward in 1736. About 200 liters of sulfuric acid per day were produced in 50 glass vessels. Ten years later (in 1746) Röbuk and Garbet significantly improved this production: instead of glass cylinders, they began to use lead chambers. Fester reported that up to 360 lead chambers were in operation at some sulfuric acid plants at that time. Only in Glasgow and Birmingham at the end of the 18th century. there were already eight such enterprises in operation.
In 1750, Home of Edinburgh discovered that sulfuric acid could be used as a substitute for sour milk for acidification in the bleaching of linen and cotton. Sulfuric acid was more profitable than sour milk. Firstly, sulfuric acid was cheaper, and secondly, bleaching with sulfuric acid made it possible to reduce the duration of the process from 2-3 weeks to 12 hours.
Unlike sulfuric acid, nitric acid began to be used much earlier in craft practice. It was a valuable product widely used in precious metal metallurgy. In Venice, one of the largest cultural and scientific centers of the Renaissance, nitric acid was used as early as the 15th century. for the selection of gold and silver. Soon other countries such as France, Germany and England followed suit. This became possible due to the fact that the greatest technologists of the Renaissance - Biringuccio, Agricola and Erker - described methods of obtaining nitric acid. According to this description, saltpeter, together with alum or vitriol, was placed in earthen flasks, which were then placed in rows in an oven and heated. The "acidic" vapors were condensed in special receivers. A similar method for the production of nitric acid was then often used in mining, metallurgy, and in the production of other chemical products by distillation. However, distillation installations were very expensive at that time, therefore, until the 18th century. they were used for other purposes. In the XVIII century. there was a huge factory in Holland that produced about 20,000 pounds of nitric acid a year. Since 1788, nitric acid, along with other products, was also produced in Bavaria (in the town of Marktredwitz) at a chemical factory founded by Fickencher.
The nitric acid production technology did not change significantly until the end of the 18th century. The retorts were made of glass and metal, often covered with enamel. From 24 to 40 retorts were placed in a special oven at once. Distinguished nitric acid of the first, second and third degree of strength. It was used for various purposes: the extraction of noble metals, when dyeing with cochineal, for processing brass, in furrying, in the manufacture of hats, engraving on copper, etc.
Before in the XVI century. hydrochloric acid was discovered, aqua regia was obtained by dissolving ammonia in nitric acid. With the help of nitric acid and aqua regia, it was possible to achieve quite high degree extraction of precious metals from ores. This phenomenon was used by alchemists as "proof" of the implementation of transmutations. They explained the increase in the yield of noble metals by the fact that as a result of transmutation, a new substance allegedly appears - silver or gold. The "experimental philosophy" that took shape during the Renaissance also attached special importance to "strong vodka"; some of the chemical processes that were carried out using this compound confirmed the atomistic views.
Libavius and Vasily Valentin also mentioned hydrochloric acid. However, the first detailed description the chemical processes for obtaining hydrochloric acid were left only by Glauber. Hydrochloric acid was obtained from sodium chloride and vitriol. Although Glauber wrote about the possibility of various areas of application of hydrochloric acid (in particular, as a seasoning for food), the demand for it was low for a long time. It grew significantly only after chemists developed a method for bleaching fabrics using chlorine. In addition, hydrochloric acid was used to obtain gelatin and glue from bones and for the production of Prussian blue.